Who is Participating?

Nope. If you're looking for a way to install software without having to write a login script that has Admin credentials in it, though, you can utilize group policy to deploy a scheduled task that can install the software with securely stored admin credentials (login scripts aren't the best way to deploy software, anyway).

If you have an MSI file to install the software, though, you can just deploy it with the Software Installation features of group policy.

Outside of those options, though, you have to utilize third party solutions (or SCCM) to install software when you don't have admin credentials on the local workstations.

I don't understand your question. A program unless told differently will run in the security context of the user. Some programs i.e. those that make system wide changes in the O/S require an additional administrator token. Most programs do not require the /runasadministrator option.